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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

28084 results found.

  1. GRB 250728A: Swift-XRT observations
  2. GRB 250728A: COLIBRÍ optical upper limit
  3. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  4. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  5. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  6. GRB 250727A: EP-FXT counterpart detection
  7. GRB 250727A: Swift-XRT observations
  8. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  11. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  12. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  13. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  14. GRB 250725A: Swift-XRT refined Analysis
  15. GRB 250725A: Fermi GBM Observation
  16. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  17. GRB 250725A: Swift-BAT refined analysis
  18. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  19. GRB 250725A: SVOM/GRM observation
  20. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  21. GRB 250725A: Swift/UVOT Upper Limits
  22. GRB 250725A: Fermi-LAT detection
  23. GRB 250725A: BOOTES-7 early optical detection
  24. GRB 250725A: SVOM/VT optical candidate
  25. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  26. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  28. GRB 250725A: Enhanced Swift-XRT position
  29. GRB 250725A: Swift detection of a burst
  30. Swift GRB 250725A: Global MASTER-Net OT detection
  31. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  32. SVOM J195836+32283 is not a real source
  33. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  34. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  35. GRB 250721A: Fermi GBM Observation
  36. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  37. GRB 250721A: Swift-XRT observations
  38. GRB 250717B: SVOM/GRM observation
  39. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  40. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  41. GRB 250721A: MAXI/GSC detection
  42. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  43. GRB 250717B: COLIBRÍ optical upper limit
  44. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  45. GRB 250717B: Swift-XRT observations
  46. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  47. Swift GRB250718.01: Global MASTER-Net observations report
  48. GRB 270713A: Kitab and AbAO Optical Observations
  49. GRB 250717B: Fermi GBM Observation
  50. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  51. GRB 250716A: Swift-XRT afterglow detection
  52. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  53. GRB 250716A: Fermi GBM Observation
  54. GRB 250714A: SVOM/GRM observation
  55. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  56. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  57. GRB 250713A: Mephisto optical upper limits
  58. GRB 250713A: SVOM/VT optical upper limit
  59. GRB 250713A: NOT optical upper limits
  60. GRB 250713A: OHP/T193 upper limit
  61. GRB 250713A: SVOM/C-GFT upper limit
  62. GRB 250706B/C: 7DT Follow-up Observations
  63. GRB 250713A: Swift-XRT observations
  64. GRB 250713A: EP-FXT counterpart detection
  65. EP250711a: COLIBRÍ continuous optical observations
  66. GRB 250706A: Swift-BAT refined analysis
  67. GRB 250702F: Swift-BAT refined analysis
  68. GRB 250628A: Swift-BAT refined analysis
  69. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  70. GRB 250713A: JinShan optical upper limits
  71. GRB 250713A: SVOM detection of a long burst
  72. EP250711a: Global MASTER-Net observations report
  73. GRB 250711A: DDOTI Optical Upper Limit
  74. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  75. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  76. GRB 250711A: SVOM/GRM observation
  77. EP250711a: NOT optical counterpart candidate
  78. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  79. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  80. GRB 250704A: GRANDMA observations
  81. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  82. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  83. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  84. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  85. IceCube-250708A: No Candidates from WINTER
  86. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  87. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  88. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  89. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  90. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  91. EP250704a/GRB 250704B: 10 GHz VLA detection
  92. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  93. IceCube-250706A: No Candidates from WINTER
  94. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  95. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  96. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  97. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  98. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  99. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  100. EP250704a/GRB250704B : HCT optical and NIR upper limits

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